In a wireless communication system, a received signal is influenced by a channel environment, and thus it is necessary to compensate for the influence of the channel environment. To do this, a predetermined pilot symbol is inserted in the time domain and the frequency domain during data transmission between a transmitter and a receiver in the wireless communication system. The receiver performs channel estimation using two continuous pilot symbols, to compensate for channel deterioration of data symbols between the two pilot symbols.
As a result, when the interval between the pilot symbols decreases, and the density of the pilot symbols increases, the channel estimation performance is improved. However, the ratio of the pilot symbols in a frame increases, which reduces information transmission efficiency.
FIGS. 1 and 2 show examples of a pilot pattern used in an existing orthogonal frequency-division multiplexing (OFDM) system.
FIG. 1 shows a pilot pattern used in a downlink partial usage of sub-channels (PUSC) mode in IEEE 802.16e worldwide interoperability for microwave access (WiMAX) standard, and FIG. 2 shows a pilot pattern used in a European telecommunications standards institute (ETSI) digital video broadcasting terrestrial (handheld) (DVB-T(H)) mode.
Referring to FIG. 1, in the pilot pattern, pilots are inserted into subcarriers, which is repeated every 2 orthogonal frequency division multiple access (OFDMA) symbols. In this structure, although sufficient OFDMA symbols are collected by the receiver to be used for channel estimation, a pilot interval is always fixed as 4 in a slot, so that in order to compensate for the channel deterioration of a data subcarrier between the pilots, interpolation has to be performed, and correspondingly performance degradation due to the interpolation cannot be avoided.
Referring to FIG. 2, in the pilot pattern, pilots are inserted into subcarriers, which is repeated every 4 OFDM symbols. In this structure, although 4 OFDM symbols are collected to be used for channel estimation, the pilot interval is always fixed as 3, so that the channel estimation performance degradation due to the interpolation cannot be avoided either.
In addition, the existing pilot pattern has a structure in which adaptive control of the channel estimation performance, granularity, channel estimation latency, and the channel estimation memory size according to the channel environment is impossible.
Therefore, a pilot pattern capable of minimizing the channel estimation performance degradation due to the interpolation while maintaining a low pilot density, and an adaptive channel estimation method using the pilot pattern are required.